This invention relates to the maintenance of idle equipment, such as internal combustion engines. Such equipment must often be used in environments which impose temperature levels on the equipment that are extremely different from the normal operating temperatures of the equipment. For instance, internal combustion engines used outdoors in northern climates through the winter are often exposed to subzero temperatures. Were the equipment to be stored at such temperatures, starting of the equipment might be impossible. At best, starting would be difficult and would subject the movable elements of the equipment to extraordinary wear. It is well known that lubrication fluids in nonoperational equipment such as engines experience a decrease in viscosity at lowered temperatures and also tend to drain from bearings and other lubricated surfaces over extended periods of time unless the equipment is periodically operated.
To counter these problems, many users of mechanical equipment in hostile or cold environments must maintain the equipment operational at all times. Internal combustion engines used outdoors are often operated or idled continuously to assure proper heating and lubrication of the equipment between periods of actual usage. Alternatively, many users of equipment such as engines, heat and pump coolant liquid through the equipment when it is not in use. Electrically heated elements and percolating heaters and valve arrangements for circulating coolant liquids through engine blocks are well known. However, heating the coolant is not satisfactory in the case of many heavy-duty engines, because the large aluminum pistons sometimes present in such engines draw such quantities of heat from the engine block that it is almost impossible to maintain a block temperature adequate to assure subsequent starting.
Another limitation of heaters that circulate coolant liquid through the block of an engine or through other equipment, is that this usually has little or no effect on its lubricating system. In an engine, the oil or lubricant normally drains by gravity to a lower pan or sump beneath the engine elements. Simply heating the engine block has little or no effect on the cold lubricant in the exposed pan beneath the block. Separate pan heaters are needed. Heating the engine block by circulating coolant fluid and heating lubricant stationary in an engine pan obviously has no lubricating effect on the engine components themselves while the engine is not in use.
The present invention was developed in an effort to maintain equipment such as internal combustion engines in operational readiness by circulating coolant or lubricating liquids through the equipment in much the same fashion as they are circulated when the equipment is operational. By substantially matching the operational circulation of such liquids, the machine elements are prelubricated when the liquid being circulated is the usual lubrication liquid. The lubricating fluid is maintained in a warm condition and the lubricated surfaces are maintained with a film of lubricant in readiness for subsequent movement. This is achieved while the normal equipment elements are stationary, and requires only a fraction of the energy that would otherwise be necessary to operate the equipment at an idle condition when not in use. Furthermore, this substantially reduces the wear on the equipment elements, since they can remain stationary while being warmed and/or lubricated.